The present disclosure relates to imaging processes, methods, and devices. More particularly, the present disclosure relates to laser printing processes, methods and devices using light controlled wettability of an imaging member.
In electrophotography, an electrophotographic substrate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging a surface of the substrate. The substrate is then exposed to a pattern of activating electromagnetic radiation, such as, for example, light. The light or other electromagnetic radiation selectively dissipates the charge in illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in non-illuminated areas of the photoconductive insulating layer. This electrostatic latent image is then developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image is then transferred from the electrophotographic substrate to a member, such as, for example, an intermediate transfer member or directly to a final recording substrate, for example, a print substrate, such as paper, or to another member. This image developing process can be repeated as many times as necessary with reusable photoconductive insulating layers.
Electrophotographic imaging members (i.e. photoreceptors) are well known. Electrophotographic imaging members are commonly used in electrophotographic (xerographic) processes having either a flexible belt or a rigid drum configuration. These electrophotographic imaging members sometimes comprise a photoconductive layer including a single layer or composite layers. These electrophotographic imaging members take many different forms. For example, layered photoresponsive imaging members are known in the art.
Photoconductive photoreceptors containing highly specialized component layers are also known. For example, a multilayered photoreceptor employed in electrophotographic imaging systems sometimes includes one or more of a substrate, an undercoating layer, an intermediate layer, an optional hole or charge blocking layer, a charge generating layer (including a photogenerating material in a binder) over an undercoating layer and/or a blocking layer, and a charge transport layer (including a charge transport material in a binder). Additional layers such as one or more overcoat layers are also sometimes included.
An exemplary known laser printing device and process 10 is illustrated in FIG. 1. Device 10 includes drum 12 having one or more layers including a photoconductive surface layer 14 and an electrically grounded conductive substrate 16. The drum 12 is electrically charged via charging device 18 and an image is projected or written onto drum 12 via laser 20, which includes mirror component 22, while the drum is rotating. A motor (not shown) engages drum 12 for rotating the drum in the direction indicated by the arrow 24 to advance successive portions of photoconductive surface layer 14 through the various processing components disposed about the path of movement of drum 12. In the areas where the light shines, the charge on drum 12 is altered thereby recording onto drum 12 an electrostatic latent image indicated by dotted line 26. Various methods are known to irradiate the charged portion of photoconductive surface 14 for recording the latent image thereon. For example, a properly modulated scanning beam of electromagnetic radiation (for example, a laser beam) can be used to irradiate the desired portion of photoconductive surface 14. Toner particles 28 are deposited by developing component 30 and the toner particles stick to charged portions of the drum 12 as indicated by dotted line 28. The developing component 30 can be, for example, a magnetic brush developer, or one of numerous types of developing components known by those skilled in the art. After the toner particles 28 are deposited onto the electrostatic latent image for development, the drum 12 advances the developed image to a transfer component 32 where a sheet of support material 34 (for example, paper) is moved into contact with the developed toner image in a timed sequence so that the developed image on the photoconductive surface 14 contacts the advancing sheet of support material 34 at transfer component 32. A charging device (not shown) can be provided for creating an electrostatic charge on the backside of support material 34 to aid in inducing the transfer of toner from the developed image on the photoconductive surface 14 to the support material 34. After image transfer to the support material 34, support material 34 is subsequently transported to a fusing component 36 that permanently affixes the transferred image to the support material 34, such as with pressure rollers 38, 40, heat, light, or a combination thereof, and a copy or print is ultimately removed by an operator. After the support material 34 is separated from the photoconductive surface 14 of the drum 12, some residual developing material can remain adhered to the photoconductive surface 14. Thus, a final processing component, such as cleaning component 42 and/or heat, can be provided for removing residual toner particles from photoconductive surface 14 subsequent to separation of support material 34 from drum 12. The cleaning component can include various mechanisms such as a simple blade or a rotatably mounted fibrous brush for physical engagement with photoconductive surface 14 to remove toner particles therefrom. The cleaning component can also include a discharge lamp for flooding the photoconductive surface with light in order to dissipate any residual electrostatic charge remaining thereon in prepared for a subsequent image cycle.
While currently available imaging systems are suitable for their intended purposes, these systems can require high voltage charging and high cost electronic components. In addition, current systems require use of dry toner which can be difficult to manage. Printing systems using electrically-controlled wetting have been proposed. However, such systems require matrices of actively electrically conducting material and controlling conductivity on an already wet surface can be difficult. Thus, there remains a need for an improved printing system and process that is energy efficient and less complex than currently available systems and processes.